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Discus 102: Breeding Discus by Willie Loh

        This is the second of three articles dealing with raising and breeding discus, Symphysodon discus and S. aequifasciatus.   The first article focused on raising discus.  This one deals with discus breeding.

Breeding Discus

The dream of most hobbyists raising discus is, of course, to breed them.  Discus have evolved a very specialized method of caring for their young.  In their natural environment, low pH produces water with very low algae and plankton populations.  As a result, discus fry feed off the slime coating produced by their parents.  A large batch of discus fry feeding off one or both parents is just about the most spectacular sight in this hobby. 

Female discus approach maturity around 12 months, while males take at least 3 months longer.  Some of the newer strains seem to take as long as 24 months to reach maturity. (A Marlboro Red I spawned three years ago just decided to pair off and lay eggs.)  Frequent water changes, a stringent tank-cleaning schedule and a high quality diet are necessary to raise discus to this stage.  Its important to realize, however, that not all fish will spawn and not all of the ones that spawn will be fertile. 

Assuming that they have been raised under good conditions, discus will usually pair off on their own.  Some people claim to be able to sex these fish.  I have had very little success and prefer to wait for the fish to sex themselves.  My approach to breeding is to keep 5 - 6 adults in a 55-gallon bare bottom tank and let them to choose their own mates.  Discus will often exhibit pre-spawning behavior, such as twitching and shaking, without ever spawning.  I usually wait for one pair to actually spawn in the large tank before moving them to their own breeder tank. 

A number of “tricks” have been suggested to stimulate breeding.  Some people use very soft water; others will drop the tank temperature down to 75^oF after a large water change.  Many people rely on special foods: white worms, black worms, earthworms, etc.  Many of these “tricks” have been used to stimulate other cichlids to spawn.  In general, tank bred discus will spawn without any specific stimulus.  Large water changes and high quality food are already a requirement for growth.  Even larger water changes and higher quality foods are not necessary.  Discus will spawn readily in very hard water, although the eggs cannot develop under those conditions.  Like many other fish, atmospheric disturbances will stimulate spawning by discus. 

Although 29-gallon tanks are most common, some breeders use 20-gallon high tanks to keep breeding pairs.  These fish do not swim particularly well and a 20-gallon tank is acceptable for smaller adults.  A 25-gallon tank is ideal for breeding because it combines a small footprint with height.  Discus tend to swim more up and down, then around and around.  Larger tanks are certainly better if space is not a consideration, as long as these tanks are tall.  It is not unusual to keep large breeding pairs in 40- and 55-gallon tanks.  If you have a pair that produces large spawns, larger tanks will be easier to manage water quality. 

Scrupulously clean tanks are an absolute requirement for breeding.  Breeding pairs are typically kept in bare bottom tanks with sponge filtration.  The only other items in the tank are a submerged heater and a spawning surface.  Even when central filtration is available, breeder tanks are isolated from the water treatment system to avoid disease transmission.  No other fish should share the tank, including Corydoras, Ancistrus and other scavenger types that may rob the spawn.  Breeding pairs are mature fish and typically require less feeding.  Spawning, and even pre-spawning behavior stimulates slime formation and these tanks need to have regular cleaning. 

In my fish room, discus have spawned on pieces of slate, inverted flower pots, glass surfaces, heaters and even occasionally, on special breeding cones.  One pair spawned on the bottom of a sponge filter.  These fish were swimming upside down, first to lay eggs, then to fertilize them.  Regardless of the spawning site, it takes the eggs 50 - 60 hours to hatch.  The wrigglers will require another 2 - 3 days before becoming free swimming.  Water changes can resume when the spawn hatches to produce wrigglers. 

For even the most jaded aquarist, the first two weeks after discus fry become free swimming is the most enjoyable aspect of the hobby.  There is very little to do except to enjoy the magnificent sight of the parents, usually darkened by heavy slime production, lead their fry around the tank.  Water change will not harm the fry and debris should be removed from the tank bottom.  Feed the parents as usual and watch them take turns, one eating and the other one nursing the spawn. 

Discus eggs require soft water to hatch, and both parents must be equally fertile to produce large spawns.  More frequent are smaller spawns (< 100 eggs) of which 35% - 50% of the eggs hatch.  I recommend adding a fungicide, e.g. Maroxy, to the tank.  Various dyes, e.g. methylene blue and malachite green, are also effective but these have astringent qualities.  If one or the other parent eats the spawn, a wire mesh cage can be fashioned to cover the subsequent spawn.  Discus will continue to fan the eggs and wrigglers through the mesh.  By the time the wrigglers become free swimming the parents have usually bonded. 

Young pairs of discus will often eat their initial spawns.  A wire mesh to protect the spawn is recommended so that the adults do not develop the habit of always eating the eggs.  Older pairs may eat small spawns or weak spawns. 

Once the fry become free swimming, they will mostly attach themselves to the parents and feed off the slime.  The fry from pigeon blood type discus may have difficulty attaching.  Explanations for this phenomenon range from reduced slime production to the inability of PB types to darken.  In these cases, the likelihood of fry attachment can be enhanced by the following techniques:

a. Line the tank with white paper.

b. Shut down or greatly reduce filtration so as to minimize disturbances in the water.

c. Drop the water level to the actual height of the fish.

d. Leave the light on.

Caring for fry is instinctual.  However, parents sometime fight and damage the fry.  One parent can be removed since either parent alone can carry the fry.  Alternatively, an egg crate divider can be inserted to separate the adults.  Sometimes, the fry will move through the divider and feed off both parents. 

The diet of baby discus can be supplemented with baby brine shrimp as early as 4 days after they become free swimming.  I typically wait 7 days before adding freshly hatched baby brine shrimp to the water.  Feeding is done by squirting the baby brine shrimp underwater toward the fry.  The baby fish will instinctively turn to feed, given their parents a 15 - 30 minute respite.  After a few feedings, the baby discus will instinctively turn away from the parents to look for brine shrimp whenever your hand breaks the water surface. 

My breeding pairs typically keep their fry for 11 - 12 days after they become free swimming. After this length of time the parents become seriously irritated with the constant nipping on their sides.  However, I have seen Asian breeders keep young discus with their parents until all the fish are feeding from live food.  If the parents decide to spawn again while the babies are still feeding, they are very likely to eat the first spawn.  If you see parents that are carrying fry begin to clean the substrate, remove the babies immediately. 

Fry can be easily removed with a siphon tube.  The young fish can be moved to a separate tank, only partially filled with water from the original breeding tank.  The smaller water volume makes it easier for young fish to find their food.  Fresh water is added gradually until the tank is full.  During this time, tank hygiene remains critically important.  Left over food must be removed from the tank bottom.  Heavy losses may occur if ammonia levels become elevated due to the large fish population so frequent water changes are necessary.  One advantage to using large breeder tanks is that it’s equally feasible to remove the parents and leave the fry to grow out. 

Young discus can be fed 10 - 12 times a day and will grow astonishingly fast if water quality is high.  Although they are small, they are also numerous.  It’s almost impossible to make enough water changes at this stage to keep up with water quality.  Water quality is also compromised by a heavy feeding schedule.  Many breeders believe that rapid progress at this very early stage determines the quality of the adult fish.  If fry are not provided with optimum growth conditions, the adult fish will never approach its genetic potential.

I use a top-loading automatic feeder (Rondomatic 600) and load live brine shrimp every morning.  Although this is an expensive feeder, live brine shrimp can be fed to these fish every two hours.  With small feedings, very little is left to die and decompose in the tank.  An automatic feeder that can provide supplemental feeding is recommended even for 6-month-old fish. 

Once the young discus get past the ½” stage, growth is a function of the quality of food and frequency of water changes.  In every spawn, some fish will grow significantly larger than their siblings.  In my experience, slow growing fish usually do not succeed.  The spawn should be culled regularly to remove weak and deformed fish, allowing the healthy ones more room to grow.  Culling is not necessarily a pleasant task.  The alternative is to have the good fish deprived of resources for the culls. 

I have been approached by a number of people with very little experience in the hobby with questions about breeding discus.  Most of them are clearly motivated by the prospect of selling young fish for $25 - $30 a piece.  After making all the investment in good genetic stock, water changes, utility charges, etc., breeding discus is seldom profitable.  Also, good breeding pairs that produce consistent spawns are rare.  Otherwise, discus would be available at angelfish prices. 

Still, breeding discus is a high point for most hobbyists.  It’s not uncommon for otherwise rational people to stay home from work, stay up all night, film and distribute footage of their first spawn.  Having pairs of discus covered with babies makes you spend a lot of time in the fish room.  Try it.  As long as you keep up with water changes, breeding discus is not that hard.